1. Field of the Invention
This invention relates to improvements in a front suspension of an automotive vehicle, and more particularly to the improvements in a front suspension of the type possessing both features of a strut type one and a double wishbone type one.
2. Description of the Prior Art
A variety of front suspensions have been hitherto proposed and put into practical use in the field of automotive vehicle. One of them is disclosed in Japanese Patent Provisional Publication No. 5178041. This front suspension is for an automotive vehicle and includes a steering knuckle (wheel supporting member) which has a lower end section which is swingably connected through a lower arm to a vehicle body (or a vehicle body-side member). A connection member is pivotally connected to the upper end section of the steering knuckle so as to be rotatable around the axis of a vertical shaft (or an installation shaft) projected from the upper end section of the steering knuckle. The connection member is pivotally connected to the lower end of a damper or shock absorber so as to be generally vertically swingable. An upper arm has one end section which is pivotally connected at a single point with the vehicle body, and another end section which is connected rotatably around the axis of a connection shaft extending generally in the fore-and-aft direction of the vehicle. More specifically, the latter end section of the upper arm is, for example, bifurcated to form two end portions which are located forward and rearward in the fore-and-aft direction of the vehicle. The two end portions are pivotally connected at respective two points with the connection member. The thus arranged front suspension is provided with advantages of both the strut type one and the double wishbone type. That is, the front suspension has an alignment similar to that of the double wishbone type one as viewed from the front of the vehicle thereby exhibiting a high stiffness against force input from a lateral direction even if the upper arm is disposed at a lower position, while has an alignment similar to that of the strut type one as viewed from a side of the vehicle thereby allowing to locate at a higher position the vehicle body-side connecting point of the shock absorber serving substantially as an upper arm thus attaining both a low stiffness in the fore-and-aft direction and a high caster stiffness. As a result, by appropriately combining both the features of the strut and double wishbone type suspensions, good ride-in comfortableness and driving stability can be obtained.
However, drawbacks have been encountered in the above-discussed conventional front suspension in which the upper arm is rotatable only around the axis of the connection shaft extending in the fore-and-aft direction of the vehicle, for example, because the upper link is connected at the two points with the connection member. That is, when the connection member is in a condition to rotate around the axis of the installation shaft upon receiving force input from the spring, the upper link does not positively make its displacement because the upper link is pivotally connected with the connection member to be allowed to make its vertical swinging movement and is pivotally connected at the single point with the vehicle body-side member. In other words, when a vertical force is input to a front wheel, the upper link makes only its vertical swinging movement, so that movements (such as a movement under distortion of an elastic bushing) other than this vertical swinging movement are restricted. As a result, the connecting points between the connection member and the upper link cannot displace in directions other than the vertical swinging movement directions when a vertical force is applied to the front suspension or when the front wheel moves vertically, i.e., under wheel stroke, thereby not positively affecting the movement of the front wheel. Therefore, it is impossible to positively change the alignment of the front suspension when the vertical force is applied to the suspension and to appropriately set change in alignment under the vertical movement of the front wheel.